This invention is related to computerized systems and methods for determining general intelligence, working memory and psychomotor functions using a portable non-invasive transcranial Doppler ultrasound, microcomputer, an operatively connected cellular telephone, and a computer-aided display. In recent years development of cognitive neuroscience has sort ways to monitor mental performance beyond the conventional neuropsychological approaches. However, monitoring mental performance has not been an easy task. Currently, there is no comprehensive and universal approach for mental performance monitoring. To address this problem more effectively, it is important to understand the basic mechanisms that underlie mental performance. The determinants of human mental performance have been the subject of intense debate for over a century. Spearman (1904, 1923, 1927) suggested that measures of performance or success in diverse cognitive tests show a pattern of almost universal positive correlation. He postulated the hypothesis of a general or g factor making some contribution to success in diverse forms of cognitive activity. This means that people with high g scores will be those usually performing well, although Spearman himself avoided the term intelligence and instead used the term g to refer to the determinants of shared variance among tests of intellectual ability (Jensen, 1987).
Snow et al (1984) constructed an idealized space in which task complexity is maximal near the center and decreases toward the periphery. Psychometric tests including Raven""s test and other complex reasoning tests were placed at the center, while simpler tests were placed toward the periphery. Applying this construct, irrespective of the views held by both hypotheses, the centrality of the Raven""s test (Raven, 1938) emerges in either case. Furthermore, it suggests that Raven""s test is a good measure of intelligence and should account for a good deal of the reasoning in other tests in the center of space (Carpenter et al., 1990). The g factor has since been interpreted as xe2x80x9cgeneral intelligencexe2x80x9d and refers to a construct underlying a small range of tests, namely those at the center of space.
The concept of general intelligence must have neural anatomic structures for processing of the information. It has been argued that the necessity of keeping several conceptual formulations in mind during Raven""s Progressive Matrices (RPM) is itself a working memory function (Carpenter et al., 1990) involving prefrontal cortex (Prabhakaran et al., 1997). Post-rolandic structures may be more critical for this task as shown in patients with brain lesions (Basso et al., 1973). Supportive evidence in normals using positron emission tomography studies have shown that high g tasks do not show diffuse recruitment of multiple brain regions, instead they are associated with selective recruitment of lateral prefrontal cortex in one or both hemispheres (Duncan et al., 2000).
Several recent studies have demonstrated that working memory is typically associated with activations in the prefrontal cortex (PFC), anterior cingulate, parietal and occipital regions (see review by D""Esposito, 2000). These brain areas received blood supply from the middle cerebral arteries. Two fundamental working-memory processes have been identified: the passive maintenance of information in short-term memory and the active manipulation of this information (D""Esposito, 2000).
Motor skill learning is associated with the activation of motor areas of the frontal lobes (Cabeza and Nyberg, 2000), notably the premotor and supplementary motor cortex (lateral and medial Broadman Area 6), and also parietal areas. All these brain areas receive blood supply predominantly from the middle cerebral arteries. Recently, studies using functional magnetic resonance imaging (fMRI) have examined motor skill learning of complex finger movements in piano players and non-musicians (Hund-Gerogiadis and von Cramon, 1999). As learning progressed, piano players showed increased activity in the contra-lateral hand area, whereas non-musicians showed decline in primary motor cortex activation. This may mean that practice-related changes in activity are influenced by pre-practice experience of the subjects.
A study on non-motor skill learning (Fletcher, Buchel, Josephs et al, 1999) investigated changes in brain activity during artificial grammar learning. As subjects learned grammar rules they relied less on memory for specific instances. Learning grammar activated left PFC, whereas reduced instance memory attenuated right PFC (Poldrack, Prabakharan, Seger, Gabrieli, 1999). The visual processing of letters by both hemispheres has been documented using the transcranial Doppler technique (Njemanze, 1996).
Currently, the use of imaging techniques such as positron emission tomography (PET) and fMRI cannot be used a single subject real-time mental performance monitoring under normal everyday conditions. Electrophysiological devices particularly the electroencephalography (EEG) has been used along with other physiological variables such as eye movement, scalp and facial muscle activity, heart activity, respiration and skin conductance to determine the state of mental performance. EEG by itself presents a complexity of parameters and along with other physiological variables have been applied to compare test standards to pretest values. The patent U.S. Pat. No. 5,295,491 to Gevins described a testing method and system for testing the mental performance capability of a human subject, which includes a digital computer workstation for presenting a test to the subject, such as visuomotor memory task. Simultaneously, the subject""s physiological variables including brain waves, eye activity, scalp and facial muscle activity, heart activity, respiration and/or skin conductance are analyzed. Test to baseline comparison of the physiological activity and scores are made to determine if the test was passed with a passing score and, if so, whether the subject, in order to pass the test, exceeded a standard based upon the subject""s normal mental effort in taking the same or similar test. Similarly, a patent U.S. Pat. No. 5,724,987 to Givens et al. described a computer-aided training system that uses electroencephalograms (EEGs) recorded from the trainee""s scalp to alter the training protocol being presented by the computer, for example to present a new task to the trainee when he or she has mastered and automatized the current task. The index of the trainee""s skill mastery and automatization is determined by analysis of the EEG using mathematical classification functions, which distinguish different levels of skill acquisition. The functions are computed by computer neural networks and consist of a combination of EEG and other physiological variables, which specifically characterize a trainee""s level of focused attention and neurocognitive workload and his xe2x80x9cneurocognitive strategyxe2x80x9d. The functions are derived either for a group of trainees, or each trainee individually, performing a battery of one or more standard training tasks while wearing an EEG hat.
The term xe2x80x9cneurocognitivexe2x80x9d has been defined as those mental functions for which physiological indices can be measured and xe2x80x9cneurocognitive workloadxe2x80x9d as the level of neural activation associated with mental effort as described in U.S. Pat. No. 5,724,987 to Givens et al. The xe2x80x9ccritical limit of neurocognitive workloadxe2x80x9d refers to a measurable cutoff point after which error rates on the task appear to rise dramatically in combination with change in neurocognitive strategy. The term xe2x80x9cneurocognitive strategyxe2x80x9d refers to the hemispheric strategy (hemisphere advantage) a subject uses to perform a task. Neurocognitive strategy is characterized by a cerebral blood flow increase in a given hemispheric region relative to the other hemisphere; it might be either in the left or right brain or bilaterally. Givens et al in U.S. Pat. No. 5,724,987 used the phrase xe2x80x9cskill acquisition and automationxe2x80x9d to denote a high degree of skill mastery in which a high level of performance and focused attention can be maintained with a relatively low level of task-specific neurocognitive workload.
xe2x80x98Mental performancexe2x80x99 refers to a cumulative physiologic brain response in a subject performing tasks of cognitive functions including linguistic, non-linguistic, visual, auditory or psychomotor stimuli. The term natural intelligence refers to mental performance in a human subject accompanied with detectable lateralization changes in cerebral blood flow velocity. The term enhanced natural intelligence systems (eNI) refers to computer programs and operating systems that are interfaced with natural intelligence in a manner that will enhance overall performance of the subject and efficiency of the programs. The term artificial intelligence refers to computer models of brain function that uses adjustable weighted connections to learn and remember. The model when organized in xe2x80x98neuronal circuitsxe2x80x99 comprising one or several neurons in a network is referred to as neural networks. A xe2x80x98hybrid neural networkxe2x80x99 is a neural set with crisp signals and weights and crisp transfer function. A xe2x80x98hybrid fuzzy neural networkxe2x80x99 is a neural network with fuzzy signals and/or fuzzy weights. A processing element of a hybrid neural net is called xe2x80x98fuzzy neuronxe2x80x99. The hybrid neural nets can be used to implement fuzzy IF-THEN rules in a constructive way. The hybrid neural nets can be trained by steepest descent methods to learn the parameters of the membership function representing the linguistic terms of the rules. The term xe2x80x98hybrid natural and artificial intelligence systems (hNI)xe2x80x99 refers to computer programs and operating systems that use fuzzy and neural network systems to process inputs of perceptual and natural intelligence to realize output of performance indices. The term xe2x80x98mental signaturexe2x80x99 refers to the highly sensitive and specific characteristics of the mean cerebral blood flow velocity changes and derived laterality indices in response to a particular task presented to a given individual and providing high reproducibility on repeated testing in the same subject. In other words, the term xe2x80x98mental signaturexe2x80x99 refers to the pattern of changes of neurocognitive strategy in response to tasks in a given subject with high sensitivity, specificity and reproducibility. The neurocognitive strategy used by a subject could describe the subject""s xe2x80x98state of beingxe2x80x99 at any given time. The neurocognitive strategy used for processing a task with the resultant best performance indices is described as the xe2x80x98best state of beingxe2x80x99. Having determined the neurocognitive strategy and workload, the proximity to the critical limit will determine the necessity to change xe2x80x9cautonomy decision-making levelxe2x80x9d from an operator to an automated system. The term xe2x80x9cautonomy decision-making levelxe2x80x9d refers to the level of independence a subject/operator has to take decisions without intervention of a xe2x80x9ccommand-and-control unitxe2x80x9d or his ability to override automated tasks on a host computer. The term xe2x80x9ccommand-and-control unitxe2x80x9d refers to a group of human operators who are involved in definition of mission strategic and tactical objectives, the term is used interchangeable with xe2x80x9cmission controlxe2x80x9d.
Prior art does not monitor in real-time general intelligence, working memory or psychomotor functions under usual conditions. The prior art electrophysiologic monitoring methods are based on multiple physiologic variables and hence increasing the potential sources of technical artifacts. The prior art based on EEG and other physiologic variables are somewhat technically impractical since the multiplicity of electrodes restricts movement and normal behavioral activity. The applicability of prior art is based on detection of change from a normative baseline that could be conditioned by a number of factors including such poorly understood areas of cognitive neurosciences such as emotion and overall consciousness. Thus, another difficulty not resolved by presently available techniques is the determination of overall rules governing neurocognitive strategy in mental performance tasks. Without such a determination of the governing rules multiplicity of factors make it difficult of make a reliable prediction based on observed physiologic change. It must also be noted that EEG based approaches are rather technically and physiologically complex and difficult to interpret for everyday applications.
There is presently no means for real-time monitoring of motor skill learning that could be easily implemented in a normal condition for example in a classroom training session. Both fMRI and PET can only be implemented for this purpose in a special circumstance and extensive preparation is required for EEG based systems. The portability of even the smallest versions of EEG remains a major obstacle to its use for monitoring under usual circumstances.
Assessment of complex perceptual learning tasks such as that during a video game in real-time under home conditions cannot be implemented with prior art. Similarly, real-time monitoring of linguistic processing during a classroom learning session could not be practically implemented with fMRI, PET or EEG. The latter instrumentations are for hospital-based conditions or specially arranged circumstances.
The issue of cost-effectiveness is a considerable and probably even an overriding factor that makes fMRI, PET and EEG-based technologies non-applicable for everyday real-time monitoring.
There is currently no method to determine the governing principles of mental performance and a unified approach to determine compromised performance other than changes to a normative baseline. Electrophysiological techniques in spite of good temporal resolution fail to define a unified set of rules governing good versus bad mental performance. Neuroimaging techniques (PET and fMRI) are cumbersome and have poor temporal resolution so are not applicable for monitoring performance in real-time man-machine interface systems. Indeed, what is required is a non-invasive technique that is easy to use for everyday applications, and would not involve extensive wiring of the subject. Such a technique must allow man-machine interface that will permit easy and fast computation of subject""s mental performance and communication to a human observer or a host computer. The said system must have high predictability of imminent compromised mental performance. The use of similar man-machine interface systems for example in modern high performance avionics may well improve overall aircraft performance and more importantly prevent aircraft mishaps due to pilot error. Such as has been described by U.S. Pat. No. 5,121,744 to Njemanze P C. For on-line monitoring in man-machine automated systems, it is essential that complexity of the variables monitored be kept low in order to minimize potential sources of artifacts or to eliminate them all together. Multi-parameter monitoring of different physiologic functions although desirable in some cases are non-specific and probably less useful compared to a pinpoint monitoring of brain blood flow velocity indices of mental performance. It is also vital to have a technique that predicts overall xe2x80x9cneurocognitivexe2x80x9d strategies allowing pre-test classification of subjects and prediction of expected results with greater specificity and sensitivity. The said neurocognitive strategy at each level of task has some specificity for each individual depending on the approach to problem solving. This can be used as a mental signature. The latter provides a unique physiologic identity of the subject as much as is his/her fingerprint by way of example. This said physiologic identity could be used when logging on a computer network. A network of several individuals making mental inputs into a computer system can then be processed using fuzzy and neural network systems as described in book by Robert Fuller entitled xe2x80x9cAdvances in Soft Computingxe2x80x94Introduction to Neuro-Fuzzy Systemsxe2x80x9d and published by Physica-Verlag, of Heidelberg, N.Y., dated 2000.
Transcranial Doppler (TCD) sonography is an ultrasound technique that uses Doppler principles to measure cerebral blood flow velocity in major brain arteries of the circle of Willis. The basic principles and common clinical applications are detailed in a book edited by Aaslid R, entitled xe2x80x9cTranscranial Doppler Sonographyxe2x80x9d and published by Springer, of Wien, N.Y., dated 1989, on pages 39 through 50. There is increasing body of evidence that cerebral lateralization can be studied using transcranial Doppler ultrasound (Njemanze, 1991; Njemanze, Gomez and Horenstein, 1992; Njemanze, 1996; Evers et al., 1999; Vingerhoets and Stroobant, 1999). Studies with TCD have been cross-validated by functional MRI (Schmidt, et al., 1999) and reproducibility assessed (Knecht, et al, 1998).
It is an objective of the present invention to provide a method and system that uses real-time measurements of cerebral blood flow velocity in major arteries of the brain for example middle cerebral arteries to measure general intelligence.
It is a further objective of the present invention to provide a method and system that uses real-time measurements of cerebral blood flow velocity in major cerebral arteries of the brain (for example the middle cerebral arteries) to make a distinction between true and false answers to a task presented to a subject.
It is a further objective of the present invention to provide a method and system for measuring working memory in order to communicate to a host computer or an interested observer for task proficiency assessment.
It is a feature of the present invention to provide a method and system for measuring working memory in order to communicate to a host computer for change of autonomy decision-making level in an automated system or mission control.
It is feature of the present invention to provide a method and system for measuring impairment of working memory in subjects or patients with memory deficits.
It is a further feature of the present invention to provide a method and system for measuring improvement of working memory due to interventional procedures or use of pharmacological agents.
It is a further feature of the present invention to obtain the physiologic parametric measure of skill acquisition and automation during mental performance of a task.
It is a further feature of the present invention to determine neurocognitive workload of a test subject in order to determine the critical limit of neurocognitive workload.
It is a further feature of the present invention to determine the hemisphere (right or left) used by a subject for processing a specific task and to determine the effectiveness of task performance, and to explain factors contributing to decrements in performance.
It is a further feature of the present invention to determine the effect of perceptual and motor tasks on mental performance for design of perceptual and motor tasks that has mutually synergistic effects on mental performance.
An object of the present invention is to determine the effect of extreme environments on mental performance. Examples of xe2x80x98extreme environmentxe2x80x99 include determining the effects of microgravity, high-altitude and deep sea diving on mental performance, and assessment of cognitive, physiologic and pharmacological methods for effective counter measures.
Another object of the present invention is to provide a computer-aided training system for subjects using real-time physiologic blood flow velocity correlate of performance as the criteria for altering the level of task difficulty presented to a subject. That could be implemented for educational, industrial and entertainment purposes.
Another object of the present invention is to provide a real-time cerebral blood flow velocity correlate of mental performance that could be integrated in videogames for upgrading or downgrading the level of task difficulty presented to a xe2x80x98playerxe2x80x99 or subject. The latter is essential for individualizing physiologic responses in videogames used on play stations for adults and children.
It is yet another object of the present invention to provide a cerebral blood flow velocity measure of mental performance on a task presented in a virtual environment generator in order to assess the different responses and optimize real-world task conditions used for design of materials including by way of example music, automobile, houses, designer clothes etc.
Yet another feature of the present invention is to provide a cerebral blood flow velocity index of performance on motor skill learning of increasing complexity in normal subjects and patients with motor impairment such as after a stroke brain lesion.
Yet another feature of the present invention is to provide a cerebral blood flow velocity index of mental performance on a visual linguistic task in healthy subjects or aphasic patients such as after a stroke brain lesion.
A further feature of the present invention is to provide a cerebral blood flow velocity index of mental performance of a visual non-linguistic task in health subjects or patients such as after a stroke brain lesion.
It is a further feature of the present invention to provide a portable instrument for monitoring mental performance that could be a personalized carry-on device for monitoring individual mental performance.
It is yet a further feature of the present invention to provide a cost-effective instrument for monitoring mental performance that could be affordable for home use.
It is yet a further feature of this invention to provide a user-friendly instrument for mental performance monitoring that is easy to operate and interpret without any specialized training.
It is a further feature of the present invention to provide a non-invasive instrument for mental performance monitoring that could be used repeatedly for several hours in a day.
It is a further feature of the present invention to provide a real-time mental performance-monitoring device that has a high temporal resolution.
It is yet another feature of the present invention to provide a mental performance monitoring device that could be connected to a network via the Internet, linking several subjects simultaneously to a host computer or mission control.
It is another feature of the present invention to provide a means to determine mental performance of workers and use the said information to organize a production process in order to improve quality management through determination and efficient use of time of maximal productivity and use of time of low productivity for recreation.
It is another feature of the present invention to determine the mental performance of workers in a production process for motion and time studies to more efficiently organize tasks by matching task difficulty to the state of mental performance.
It is another feature of the present invention to determine mental performance for use in personal organization of schedule and programs, to maximize use of periods of the day with highest mental performance to perform the most mentally demanding tasks.
It is another feature of the present invention to determine the mental performance for understanding of an individual""s biorhythm with exact determination of periods of the day with highest efficiency and those with lowest efficiency dependent on the circadian rhythm of the individual.
It is another feature of the present invention to determine the mental performance of subjects on a mission in order to assess the mental health status of the individuals, their exact location and the capacity to accomplish the mission.
It is yet another feature of the present invention to determine mental performance of a subject and communicate it via a cellular phone to a host computer for mission control.
It is another object of the present invention to determine the mental signature of a given subject that could be used as a personal physiologic identity when logging on to a network of restricted access.
It a further object of the present invention to use the mental signature of a subject to provide computer network security including financial, military, top government computer network and major businesses.
It is a further object of the present invention to process mental performance of several subjects making an input in a computer system using fuzzy and neural network systems for optimization of the production processes.
It is a further object of the present invention to process mental performance of a subject making an input in a computer system for mental signature recognition.
It is a further object of the present invention to process mental performance of a subject making an input in a computer system for recognition of best state of being.